Utilizing a 490 Micro GC with a TCD and MolSieve 5A 20 m column we are attempting to determine the purity of our plant's nitrogen as Airgas( run the nitrogen generation plant on site) can not provide chromatography or proof of the 99.99% purity of their nitrogen. We were told by the sales rep that the 490 micro GC can see down to the 5ppm levels of CO and O2 in nitrogen, but we have yet to obtain even a peak at 10ppm of either in a nitrogen balance. Below is the system parameters we are currently running:

I increased to 800 saw some additional humps when running the 10 ppm (O2 and CO) standards. I then reran at max inj time of 999ms and will take a look at the data today. Thanks for you help and will post results and maybe some chromatography.

Agree with Remko. Increase column temperature. All peak will come out much quicker and as a result they are more narrow and thus higher. This is especially helpful when analyzing late eluting components like CO on a Molesieve column.

So I have increased the oven temp to 80C and changed it over to continuous flow at Agilent's suggestion and I have a CO peak at 10ppm. I still however do not have an oxygen peak. I recently found an old O2 and CO in balance of He gas std and ran that. It showed the oxygen peak, if visible will elute under my N2 peak. Any suggestions on forcing this out earlier or later?

So after trying out some of the suggestions here and working with agilent it has been determined something else is up with the instrument and have been advised to send the micro GC in to bench repair. So thanks for all the help. Hopefully when I get it back I will not be back on here posting the same problems.